Meter Tails Query

[afswift]

Hi,

If i move a consumer unit and the new tails will be about =7m - 8m long do i need an 100A switchfuse unit or do i just need a 100A isolator after the meter before the long run?

Cheers, Adam

 

[Adam_151]

You need to ask the local DNO what length of tails they will allow their service to fuse to protect, a lot of them will say 3m, but it could well be longer for your DNO.

Go beyond what the DNO allow their service fuse to protect and you'll have to install your own switchfuse, keeping the tails upstream of the switchfuse below the maximum length given by the DNO,... beyond the switchfuse, thats your own submain and BS7671 applies

No need to have a separate isolator outside of the main CU/ switchfuse unless you need one to be able to have a single isolator for the installation (ie. you have two CUs connected into service connnector blocks)

 

[ban-all-sheds]

Probably the former, but check with your DNO - requirements vary.

You might well have to mechanically protect the tails as well.

How do you intend to isolate the supply to be able to do this safely?

What are you going to do about the change in length of all the circuit cables?

What are you going to do about testing, and notification?

 

[afswift]

Hi thanks for the replies.

I am intending to do this work as one of my assessments to join NICEIC,

I am in the process of notifying the work via LABC, i will be testing and providing a BS7671 certificate.

I have my own test gear, which is just out of calibration but will be calibrated before i test. (fluke 1653)

Is their anything else i need to take into account?

Cheers, Adam

 

[afswift]

oh and currently we have a three phase supply coming into the house,

I was thinking of getting the DNO to come and change to SP, does anyone know what approx cost would this be?

If they are changing the supply, i could provide the switchfuse for them to connect into, which would leave a safe way for me to isolate the supply.

If not do they have to come out to pull the main fuse, or do i just need to contact them to let them know what i am doing and get permission to cut the seal?

Adam

 

[ban-all-sheds]

I was thinking of getting the DNO to come and change to SP, does anyone know what approx cost would this be?

Out of all proportion to the work involved.

If they are changing the supply, i could provide the switchfuse for them to connect into, which would leave a safe way for me to isolate the supply.

You could, but they might not do it. Is yours one of the ones that will provide an isolator themselves, if requested?

If not do they have to come out to pull the main fuse,

That's the theory, but some are relaxed about qualified electricians doing it.

or do i just need to contact them to let them know what i am doing and get permission to cut the seal?

The problem then is what happens if permission is refused?

It might be an idea to see if you can find out from their website what their policy is.

 

[afswift]

Spoke to the DNO today and they will come out and change the metering to single phase and connect up my new tails when they are installed.

He said he thought it would be free, gonna confirm it tomorrow.

Can i run the tails in between the upstairs floor void and drop them down to the new CU location or do they need additional protection?

Adam

 

[afswift]

Both the regs (16th and 17th) state that the wiring will be ok in the floor as long as the void is such that the cables can be positioned in such a way as they are 50mm from both the upper floor and the ceiling below.

Iam i reading this regulation correctly, it is reg 522-06-05 in the 16th

Please could some one clarify this. And will this apply as well to the tails?

Adam

 

[Adam_151]

The DNO might have additional requirements for the tails, its their fuse you are using to protect them (acceptable by BS7671 as long as they give their permission), so they have to put some limits on it to ensure that the protection is effcetive, the most common one is a lot of DNOs limit you to 3m/4m of tails.

I wouldn't be at all supprised if they said you couldn't run tails protected by their fuse in floor voids, actually, but see what they say

 

[afswift]

I am intending to put a fused isolator either either 80 or 100a within 1m of the meter then run the tails about 8m under the floorvoid.

 

[Adam_151]

I am intending to put a fused isolator either either 80 or 100a within 1m of the meter then run the tails about 8m under the floorvoid.

From your switchfuse onwards, you can do whatever you like as long as you comply with BS7671

Not sure DI tails and an earth are the best cable type to use though... SWA might be better?

 

[afswift]

I know it maybe better to use swa, but i am mounting a plastic mk santry cu in the front porch for the neat appearence i really want all the cables to run in from the back, SWA would be a pain to terminate.

As long as i run the tails complying with the regs, do you think this will be acceptable?

Will be using this job for my NICEIC initial assessment.

Cheers, Adam

 

[DESL]

Split concentric from switch fuse to CU is a good alternative to SWA and it will be fairly simple to bring through the rear of CU to terminate.


//www.diynot.com/wiki/electric...bles_straight_concentric_and_split_concentric